physics final part 2

a 1 kg glider and 2 kg glider both slide toward each other at 1 m/s on an air track. They collide and stick. The combined mass moves at

1/3 m/s

a machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is

10% 1000w/100w= 10%

two identical particles move toward each other. Just before they collide one has a kinetic energy of 25 J and the other 75 J. At this instant their total KE is

100 J 25+75 =100 J kinetic energy can add

a toy elevator is raised from the ground floor to the second floor in 10 seconds. The power needed using 1000 J of work is

100 W

an astronaut (50kg) floating alone in outer space throws baseball (1kg). If the ball moves away at 20 m/s, calculate the speed of the astronaut

1000 m/s ????

the mass of a ball moving 3 m/s with a momentum of 48 kg m/s

16 kg

the mass of a ball moving at 3 m/s with a momentum of 48 kg m/s is

16 kg 48/3 = m3/3 16=m

1 mile = how many meters (roughly)

1600 m

the circumference of bike wheel is 2m. If it rotates at 1 rev per second then its linear speed is

2 m/s

The average braking force of a 1000 kg car moving at 10 m/s braking to a stop in 5 s is

2000 N

the average breaking force of 1000 kg car moving 10 m/s breaking to stop in 5 s is

2000 N braking force = mXv/t 1000(10)/5 = 2000N

speed of 4kg ball with momentum of 12 kg m/s

3 m/s

the speed of a 4kg ball with a momentum of 12 kg m/s is

3 m/s

one kilowatt- hour represents

3.6 million joules

danny weighs 500 N and steps off a diving board 1m above the water. Danny hits the water with KE of

500 J KE= 1/2 mv^2 KE= 1/2 (500)(10)^2 w= fd 500(1)= 500 J

what is the force of gravity on a 500 N woman standing on earths surface

5000 N

two 5000 kg rail cars without friction (one at 1 m/s, the other at 2 m/s) toward each other on a level track. They collide, couple, and roll together with a combined momentum of

5000 kg m/s

the change in momentum that occurs when a 1 kg ball traveling at 4 m/s strikes a wall and bounces back at 2 m/s is

6 kg m/s

if you're on a ferris wheel seated 10m from the ferris wheels axis that makes a complete rotation each minute your linear speed is

62.8 m/min v=rw v=10(2pi)

the work done in pushing a TV set a distance of 4m with an average force of 20 N is

80 J w=fd w=20(4)= 80 J

it is correct to say that impulse is equal to

a corresponding change in momentum - impulse is proportional to momentum

if alex wishes to rotate his skateboard, then he must apply a a. torque b. rotational manuver

a torque he needs to apply a force on the ends of the skateboard in order to rotate it

a block of ice (2 kg) at speed 2 m/s slides on a table that has a height of 3m a. calculate the total mechanical energy of the block just before it leaves the table b. use conservation of energy to calculate the speed of the block just before it hits the ground

a. 12 J b. 6 m/s look up on chegg

a 1kg ball dropped from 2m rebounds only 1.5 m after hitting the ground. a. what is the KE of the ball just before and just after it hits the ground b. what amount of energy is converted into heat and other forms of energies?

a. 3 J b. all of the energy is converted because energy doesn't disappear

a 1.0 kg ball traveling at 4 m/s strikes a wall and bounces back at 2.0 m/s a . what is the momentum of the ball before it hits the wall? b. calculate the change in momentum for the ball

a. 4 kg m/s b. 2 kg m/s

two blocks move on ice. left block= 2kg with 2 m/s right block= 3kg with 1m/s a. what is the total momentum of the system? b. After the collision, 3kg block moves with 1.5 m/s what is the velocity of the 2kg block?

a. 7kg m/s b.1 m/s because the velocity decreases

two identical gliders slide toward each other on a air track. one moves at 1 m/s and the other at 2 m/s. They collide, stick, and moves. The mass of one cart is M kg a. Write an expression for momentum of each cart. Note that your answer will contain M b. User conservation of momentum to find the speed of the combined carts

a. p=m(2) p=m(1) b. 3 m/s

a hydraulic jack is used to lift objects such as automobiles. The input force (f) is 200 N over a distance of 1 meter a. what is the work done by the input force b. calculate the output force over a distance of .2 meters

a. w= 200 J b. 200 J/.2 = f(2m/.2= 1000F

a. how much work is done when you push a crate across a 20 m floor with a horizontal 100 N force? b. if the force of friction is a steady 50 N, show that the KE gained by the create is 1000 J c. show that 1000J of energy is turned into heat

a. w=fd w=100N (20m) w= 2000 J b. force friction = 50N 100-50=50 N KE= 50N(20m)= 1000 J gained

a circus diver drops from a high pole into water far below. When he is halfway down a. his pe is halved b. he has gained an amount of ke equal to half his initial pe c. his ke and pe are equal d. all above

all ! pe decreases going down we gain ke so halfway means 1/2 pe and 1/2 ke

a car traveling along the highway brakes to a stop over a certain distance. More braking force is required if the car has a. more mass b. more momentum c. less stopping distance

all of the above more mass= more momentum more mass means you need greater speed which would take longer to brake

solid cylinder will roll down incline with greater ______ than a hollow cylinder

any solid cylinder will roll down any incline with greater acceleration than any hollow cylinder, regardless of mass or radius

both rotational inertia and torque involve distance from the

axis of rotation

bigger radius= ______ speed

bigger

The bob of a simple pendulum has its max KE at the

bottom of its swing

stand a broom upright at the end of its pole and let it topple to the floor. repeat but with the bristle end on the floor. The faster fall will be the broom on its

bristles because the mass is closer to the center so it falls faster

to make a profit a buyer purchases metal by weight at one altitude and sells it at the same price per pound at another altitude. The supplier should buy a ______ altitude and sell at a ______ altitude

buy a high altitude and sell at a low altitude

a coin and ring rill down an incline at the same time , the first to reach the bottom is the

coin because it is easier to rotate

the net force exerted on a cart traveling in a circular path at constant speed is

directed toward the center of the curve

the net force exerted on a car traveling in a circular path at constant speed is directed towards _______

directed towards the center of the curve - if acceleration pointing center- force is pointing center

double R = _______ v

double

if a turn table's rotational speed is doubled, then the linear speed of a pet hamster sitting on the edge of the record will

double

suppose you take a sharper turn than before and halve the radius, by what factor will the centripetal force need to change to prevent skitting?

double

double angular = ________ linear

double angular = double linear 2xw=2xv

when the force that produces an impulse acts for twice as much time, the impulse is

doubled

hampster sits on record player that has angular speed. If the hamster moves to a point twice as far from the center, then its linear speed a. doubles b. halves c. remains same

doubles

when the speed of an object is doubled, its momentum

doubles ex. p=mv p=(5)(5)= 25 p= (5)(10)= 50

the unit kilowatt- hour is a unit of a. energy b. momentum c. power d. time

energy

hoop has mass far/close to the axis

far

solid cylinder starting from rest will roll down an incline faster/ slower than a hoop

faster

the total momentum of a flock of identical birds could be zero only if the birds are

flying in different directions

a fast moving car hitting a haystack or hitting a cement wall produces vastly different results a. do both experience the same change in momentum? b. do both experience the same impulse? c. do both experience the same force?

for both the wall and hay your momentum is brought to zero by the same impulse. you extend the time during which your momentum is brought to zero. A longer time interval reduces the force and decreases the resulting deceleration.

if you place a pipe over end of range when trying to rotate a bolt, effectively making the wrench handle twice as long, you will multiply the torque by

four 2x force + 2x radius = 4x

suppose you double the speed at which you round a bend in the curve, by what factor must the cf change to prevent you from skitting

four times

greater rotational inertia has ____ resistance to change in motion

greater

hoop has _______ rotational inertia and is harder to start rolling

greater

according to Newton, the greater the masses of interacting objects, the ____________ the gravitational force between them

greater the gravitational force between them

half radius = _______ speed

half

consider a string with several rocks tied around its length at equally spaced intervals. you whirl the string overhead so that the rocks follow circular paths. compared with a rock at the end of the string, a rock in the middle moves

half as fast

a block of ice sliding down an incline has half its maximum kinetic energy a. at the top b. at the bottom c. halfway down d. need more info

halfway down

inner = _______ radius

higher

angular (w) means

how much angle it will cover in 1 second

linear (v) means

how much distance it will travel in 1 second

conservation of angular momentum

if no external net torque acts on a rotational system

padded dashboards are safer than non padded because the passengers hitting the dashboard encounter

lengthened time of contact - time is longer

each rolling wheel for RR train is tapered. Compared with the wide part and narrow part of the wheel has a tangential speed that is a. less b. greater c. same for both

less

show the mass of the box is 5 kg when leg of string is 2m, string tension is 10 N & tangible speed of puck is 2 m/s

m= (10) 2/ 2^2 = 5 kg

a same size iron ball and wooden ball are dropped simultaneously from a tower and reach the ground at the same time. The iron ball has a greater

momentum

long baseball bat help near narrow end has more/less rotational inertia than a short bat

more

horses with greatest liner speed on a merry go round are located

near the outside

an industrial flywheel has greater rotational inertia when most of its mass is

near the rim

a falling 1 N apple hits the ground with a force of about a. 1 N b. 2 N c. 4 N d. 10N e. need more info

need more info

when Peter tosses an egg against a sagging sheet, the egg doesn't break due to a. reduced impulse b. reduced momentum c. both d. neither

neither

a light aluminum ball and a heavy lead ball of the same size roll down an incline. When they are halfway down the incline they will have identical a. KE b. PE c. momentum d. inertia

none halfway can't have identical because they're different weight and PE is decreasing while KE is increasing

a sandbag motionless in outer space is hit by a three times as massive sandbag moving at 12 m/s. They stick together and move at a speed of a. 3 m/s b. 4 m/s c. 6 m/s d. 8 m's e. none above

none above

train the outer turn takes longer or shorter from inner turn?

outer takes longer

both is more likely to turn when the applied force is ________ to the handle

perpendicular

tangential speed depends on

radial distance (distance from the axis)

run with legs bent you increase/reduce rotational inertia

reduce

when railroad tracks make a curve the outer tracks are longer. this means a wheel on the outer track needs to

roll faster than the wheel on the inner track

compared with a force, a torque involves:

rotation, leverage, and distance from axis rotation

tangential speed is directly proportional to?

rotational speed at any fixed distance from the axis of rotation

merry go round cover _________ angular speed and ________ linear speed

same angular and dif linear

level arm is the _____ distance between the axis of rotation and the line along which the force acts

shortest

which requires the most amount of work by the brakes of a car? a. slowing down from 100 km/h to 70 km/h b. slowing down from 70 km/h to a stop c. equal amounts for both

slowing down from 100 km/h to 70 km/h

compared with falling on a stone floor, a wine glass may not break when it falls on a carpet floor because the

stopping time is longer on the carpet

the rotational inertia of your leg is greater when your leg is

straight

calculate the torque produced by a 50 N force when a pipe extends the length of the wrench to .5 m

t=rf t= .5x 50 t= .25 Nm

which jar will roll down an incline in the shortest time, an empty one or one filled with peanutbutter

the filled jar because the mass is closer to the center rotating axis

to catch a fast moving ball, you extend your hand forward before contact with the ball and let it ride backward in the direction of the balls motion. Doing this reduces the force of contact on your hand principally because the

time of contact increases - longer time less force

a freight train rolls along track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is

twice

twice radius= ________ speed

twice

two identical arrows, one with twice the KE of the other, are fired into a bale of hay. Compared with penetration of the slow arrow, the faster arrow penetrates

twice as far - 2xKE= 2x distance KE is in motion, so twice the KE requires twice the distance

the work you do when pushing a shopping cart twice as far while applying the same force is

twice as much 2x distance means 2x work

linear speed equation

v=rw linear speed= radius x angular speed